Carrier current system



' Sept25, 1945. J, L. WOODWbRTH 2,385,673

CARRIER CURRENT SYSTEM Filed July 27, 1943 Fig.1,

/ TRANSMITTER Elk His Attorney.

Patented Sept. 25, 1945 I UNITED STATES PATENT OFFICE CARRIER CURRENT SYSTEM John L. Woodworth, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application July 27, 1943, Serial No. 496,299

7 Claims.

The present invention relates to a carrier current system for application to a plurality of interconnected feeders each having a carrier current transmitter and one or more carrier current receivers. In such systems it is desirable that the carrier current transmitter for one of the feeders affect only the receivers associated with that feeder, particularly in the case where the receivers are relays for carrying out switching operations.

' Under some circumstances it has been found.

that the carrier current voltage at the interconnection of the feeders from one of the, transmit ters is sufiiciently great to affect receivers associated with another of the transmitters.

stood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 represents a carrier current system embodying my invention; Fig. 2 is a modification of the transmitter for substitution in Fig. l; and Fig. 3 represents another carrie current system.

Referring to Fig. 1 of the drawing there is shown a carrier current system comprising transmitters I and 2 and receivers 3 and 4 respectively primary windings l I of the coupling transformers which parallel tune the coupling transformers to serve as wave traps. The parallel tuning of the coupling transformers presents a high impedanceto carrier current voltages fed from one of the transmitters through the interconnecting power transmission line to a feeder associated with the other transmitter. For example, under the condition under which the transmitter l is sending and the transmitter 2 is idle, the carriercurrent voltage from the transmitter I encounters a high impedance at the coupling transformer of the transmitter 2 and accordingly cannot affect the receiver 4. For effective operation it is obviously necessary that the transmitters be arranged intermediate the associated receivers and the interconnection between the feeders.

The system of Fig. 1 does not provide protcc tion for the case in which the transmitters I and 2 are'simultaneously energized. For this condition, which may occur at infrequent intervals,

the parallel tuning of the coupling transformers is impaired by the parallel circuit through condenser lfl, key 9, and generator 8, and the carrier current voltage from on of the transmitters may affect a receiver associated with the other transinitter.

stituted for either of the transmitters in Fig.1.

the coupling transformer 12 is shunted by two parallel circuits each of which includes a conassociated with feeders 5 and 6 interconnected by a power transmission line I. l and 2 operate at or near the same carrier frequency and are intended to control only the re-' ceivers 3 and 4 respectively. Each of the transmitters comprises a generator 8 connected through a key 9 and a blocking condenser 10 across the primary ll of a coupling transformer I! having a secondary l3 connected in series with one of the feeders 5 or 6. When one of the keys 9 is closed, a carrier current voltage is impressed onthe associated feeder through the coupling transformer and provides the signal for operating the associated. receiver. A carrier .current voltage is also impressed across the impedance of the circuit comprising the power generator 35 and the interconnecting power transmission line 1 and, while the voltage across the power transmission line is generally small, it is under some conditions sufficient to result in the impression of The transmitters denser M or iii and one of the poles I6 or H of a two-pole keying switch l8. The carrier current generator 8, which has an inductance 'represented at I9, is connected across one of the poles H of the keying switch so that the generator is shorted when the keying switch is closed. When the keying switch is closed, the condensers H and I5 in parallel tune the coupling transformer I! as a wave trap. When the keying switch is open, the circuit through the condenser H is opened and the condenser I5 is connected in series with the generator 8 across the primary winding H. The condenser l5 parallel tunes the coupling transformer as a wave trap. With the transmitter of Fig. 2 the coupling transformer I2 is at all times tuned as a wave trap to prevent interference due to other carrier signals.

. 'In-the modification shown in Fig. 3 feeders 20 and 2|, having respectively associated therewith erator 28 having an inductance represented at 30 connected through a keying switch 3| and a series circuit including condensers 32 andinductance 33 across the feeder conductors. The

keying switches 3| have two positions, one con- This disadvantage is overcome by the transmitter shown in Fig. 2 which may be submy invention.

erator so as to impress a carrier current. voltage fromthe generator across the respective feeder,

and the other position in which th'ecircuit to the generator is opened and the keying switch is closed on an inductance 34,'having the same value as the inductance 30, which completes an sisting of the condensers 32, inductance l3, and either of identical inductances 30 or 34. These alternative series circuit across the" respective feeder. In either position of the keying switch there is a series circuit across the feeders con- 1 series circuits are tuned for resonance at the carrier current frequency and accordingdy short circuit carrier current voltages fed to the respective feeders from the transmission line 26.v Since the transmitters are located intermediate the associated receivers and the interconnecting transmission line 26, a carriercurrent-voltage fed from one of the transmitters through the interconnecting transmission lineto another feeder is short circuited by the seriescoupling circuit associated with that feeder. This prevents undesired operation of one of the receivers by signals from a transmitter associated with another feeder.

Itis importantthat the coupling circuit be i tunedso as to short circuit thepundesired carrier voltage at the points of connection of the series circuit to the feeder. If the tuning of the series circuit were such as to provide series resonance at carrier frequency for the circuit, which also included the feeder to the'assocl'ated receiver,

under some conditions. the series circuit associated with the transmitter would increase rather than decrease interference due to'carrier voltages fed through the interconnecting trans mission line 26.

While I have shown particular embodiments of my invention. it will be understood that many modifications may be made from the spirit thereof, and the appended claims to cover tions as fall within without departing I contemplate by any such modifiesthe true'spirit and scope of desire to secure by States, is.

What I claim as new and Letters Patent of theUnited 1. In a carrier current system for a' power sys-Z tem including a plurality of feeders, a carrier rent transmitter associated with each of said.

feeders, each said transmitter including a carrier nested inseries with the carrier current gene 'rent signals from another source in both open and closed positions of the keying switch.

3. In a carrier current system. a feedercon nected to,,.a power system, a carrier current receiver associated with the feeder, a carrier current generator having a predetermined inductance, a series resonant circuit shunted across the feeder intermediate the receiver and the power system for short circuiting signalsof car-v rier current from the power system and thereby preventing false operation of the receiver, saidnected to a power system, a carriercurrent receiver associated with the feeder, a carrier cur-j rent generator having a predetermined induc tance, a series resonant circuit shunted across the feeder intermediate the receiver and thepower system for short. circuiting signals of carrier current from the power system and thereby A preventing false operation of the receiver, said series circuit including a keying switch in one position connecting the generator as part of the circuit and in another position disconnecting the generator and connecting an inductance. of said predetermined value as part of said circui 5. In a carrier system, a coupling transformer having a secondary for connection in series with a feeder and a primary having shunt connected tuning means, switching means for connecting the carrier current generator to said primary and for switching said tuning means so that the transformer is a parallel tuned trap for carrier current signals from another source when the generator is either connected to or. disconnected from said primary.

6. In a carrier current system for a power system including a plurality of interconnected feeders, a carrier current receiver and a carrier cur-- current generator, means for coupling said generator to its feeder intermediate the associated receiver andthe interconnection of said feeders,

two-position keying means for selectively disabling said transmitter or rendering said transmeans'including a resonant circuit tuned to the carrier current frequency for selectively 0011-" nesting each said transmitter to the associated feeder at a point intermediate the connected receiver and. power system, the resonantcircults associated with non-selected feeders serving as wave traps for signals of carrier frequency fed through the power system from selected transmitters thereby to render receivers connected tench-selected feedersmon-responsive to carrier current signals on selected feeders.-

2. In a carrier current system, a coupling transformer having a secondary for connection in series with a feeder and aprimary'shunted by two parallel circuits, each circuit including a parallel tuned as a wave trap for carrier curmitter operative to'impress a carrier current signal upon the associated feeder, and means including said coupling means for tuning each said transmitter as a wave trap for undesired carrier current signals from any other transmitter through said interconnection in both positions of said keying means. I

' '1. In a carrier current system .for a power system including a plurality of interconnected feeders. a carrier current receiv'enand a carrier current transmitter associated with each feeder. each said transmitter including a carrier current generator, means for coupling each said generator toits feeder intermediate the associated receiver and the interconnection of said feeders, and keying means for selectively disconnecting each said generator or connecting said generator to impress a carrier current signal upon its feeder, said keying means including switching means for tuning the associated coupling means alone as a wave trapwhen said generator is disconnected and tuning said coupling means and a generator together as a wave trap when said generator is connected to its feeder, thereby to preclude the reception of signals by any receiver through said interconnection.

' JO HN L. WOODWQBTB, a, 

